The effects of short term cytokine exposure on cord blood stem cells

Problem: Evaluate the effects of shea term cytokine exposure on cord blood (CB) stem cells. Methods: CB CD34(+) cells were incubated for 7 days with either 1) IL1 + IL3 + SCF, 2) IL3 + IL6 + G-CSF + SCF, 3) SCF, 4) flt3L or 5) SCF + flt3L, and evaluated for progenitor and stem cell content (Long Term Haematopoietic Culture-Initiating Cell [LTHC-IC]), nucleated cell count, immunophenotype and resistance to 5-Fluorouracil (5FU, quiescent progenitor content) before and after cytokine-mediated expansion. Results: Cells stimulated with IL3 + IL6 + G-CSF + SCF produced significantly greater numbers of nucleated cells as compared to other cytokine combinations. Cells stimulated with IL1 + IL3 + SCF or IL3 + IL6 + G-CSF + SCF produced a significant increase in myeloid progenitors but no change in CD34(+) cells, 5FU resistant quiescent progenitors or LTHC-IC as compared to input values. Cells stimulated with SCF had the highest frequency of CD34(+) and progenitor cells. The frequency of LTHC-IC was less than input for all incubations, but was significantly higher with SCF 2.27 +/- 0.5% (p = 0.017) than with any other cytokine combination. Conclusions: Our results suggest that single early-acting cytokines may be more appropriate for the stimulation of CB stem cells because they maintain a greater frequency of cells with both phenotypic and functional characteristics of stem cells.